datafort_joins Module

DataFort Joins Module

This module provides standalone join and merge functions for data frames. All functions take a data_frame as the first argument instead of being type-bound procedures.

Functions

Join Functions

• df_inner_join(df1, df2, key_col1, key_col2) - SQL-style inner join
• df_left_join(df1, df2, key_col1, key_col2) - SQL-style left join
• df_right_join(df1, df2, key_col1, key_col2) - SQL-style right join
• df_outer_join(df1, df2, key_col1, key_col2) - SQL-style outer join (full outer join)

Merge Functions

• df_merge(df1, df2, on_column, how) - Merge using column names

Notes

• All join functions return a new data frame
• Key columns must have the same data type (integer, real, or character)
• Right table columns are suffixed with “_right” to avoid name conflicts
• For merge, the ‘how’ parameter can be: “inner”, “left”, “right”, or “outer”

Functions

public function df_inner_join(df1, df2, key_col1, key_col2) result(joined_df)

Perform an inner join between two data frames

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Arguments

Type	Intent	Optional	Attributes		Name
type(data_frame),	intent(in)			::	df1
type(data_frame),	intent(in)			::	df2
integer,	intent(in)			::	key_col1
integer,	intent(in)			::	key_col2

Return Value type(data_frame)

public function df_left_join(df1, df2, key_col1, key_col2) result(joined_df)

Perform a left join between two data frames

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Arguments

Type	Intent	Optional	Attributes		Name
type(data_frame),	intent(in)			::	df1
type(data_frame),	intent(in)			::	df2
integer,	intent(in)			::	key_col1
integer,	intent(in)			::	key_col2

Return Value type(data_frame)

public function df_merge(df1, df2, on_column, how) result(merged_df)

Merge two dataframes on column names (similar to SQL join but using names)

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Arguments

Type	Intent	Optional	Attributes		Name
type(data_frame),	intent(in)			::	df1
type(data_frame),	intent(in)			::	df2
character(len=*),	intent(in)			::	on_column
character(len=*),	intent(in)			::	how

Return Value type(data_frame)

public function df_outer_join(df1, df2, key_col1, key_col2) result(joined_df)

Perform an outer join between two data frames

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Arguments

Type	Intent	Optional	Attributes		Name
type(data_frame),	intent(in)			::	df1
type(data_frame),	intent(in)			::	df2
integer,	intent(in)			::	key_col1
integer,	intent(in)			::	key_col2

Return Value type(data_frame)

public function df_right_join(df1, df2, key_col1, key_col2) result(joined_df)

Perform a right join between two data frames

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Arguments

Type	Intent	Optional	Attributes		Name
type(data_frame),	intent(in)			::	df1
type(data_frame),	intent(in)			::	df2
integer,	intent(in)			::	key_col1
integer,	intent(in)			::	key_col2

Return Value type(data_frame)

Subroutines

private subroutine build_joined_dataframe(df1, df2, indices1, indices2, num_rows, result_df)

Helper subroutine to build joined dataframe from match indices

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Arguments

Type	Intent	Optional	Attributes		Name
type(data_frame),	intent(in)			::	df1
type(data_frame),	intent(in)			::	df2
integer,	intent(in),		dimension(:)	::	indices1
integer,	intent(in),		dimension(:)	::	indices2
integer,	intent(in)			::	num_rows
type(data_frame),	intent(out)			::	result_df